1. Field of the Invention
The present invention relates to an electrophotographic printer and in particular, an electrophotographic printer wherein an attachable and detachable mechanism of a photoconductive drum is improved.
2. Description of the Related Art
In general, the photoconductive drum of an electrophotographic printer is configured as disclosed in e.g. JP-A No. 502130/1990. The configuration is explained in reference to FIGS. 9 and 10.
A photoconductive drum 1, configured in a cylindrical shape, engages with the outer circumference of a first flange 3 fixed to a step formed between a drive shaft 2 and a small diameter part 2S of the drive shaft 2 on the side of an end of the cylinder in a electrophotographic printer. Meanwhile, the end on the other side of the cylinder engages with a second flange 4 attached to the small diameter part 2S of the drive shaft 2.
Then the photoconductive drum 1 is concentrically supported on the drive shaft 2 and firmly retained between the first flange 3 and the second flange 4. A tightening means 5 such as a nut screwed at an end of the small diameter part 2S tightens the first flange 3 and second flange 4. Also, the first flange 3 is integrally provided with plural ribs 3R that extend in the axial direction and the end of the ribs 3R is located close to the second flange at the time of tightening. The ribs 3R function as a guide means so that the photoconductive drum 1 may not contact peripheral devices when the photoconductive drum 1 is attached to or detached from the drive shaft 2.
In addition, a retaining means 6 is attached so as to contact plural portions located in the circumferential direction on the inner circumferential face of the photoconductive drum 1 in order to prevent distortion of the photoconductive drum 1. The retaining means 6 is provided with halved support pieces 6A and 6B having plural contact parts contacting the photoconductive drum 1. And spring members (not shown in the figures) to press the support pieces 6A and 6B into contact with the photoconductive drum 1 by spring pressure.
The electrophotographic printer has the retaining means inside the photoconductive drum and the photoconductive drum is replaced together with the retaining means when it is replaced. From the view point of resource conservation therefore, the retaining means has been discarded in vain.
To cope with the problem, it is one solution to reuse a retaining means by dismantling the retaining means from an old photoconductive drum and then attaching the dismantled retaining means to a new photoconductive drum at the time of the replacement of the photoconductive drums. However, photoconductive drums are replaced by end-users in almost all cases, furthermore special tools are used for detaching or attaching the retaining means from or to a photoconductive drum, and hence the replacement of the photoconductive drum is very difficult and needs a long time.
An object of the present invention is to provide an electrophotographic printer capable of easily attaching and detaching a retaining means to retain the inside of a photoconductive drum to and from the photoconductive drum.